1. Field of the Invention
The present invention relates to a device control apparatus and method, a client apparatus, and a device control system, and more particularly to a device control apparatus equipped with a function for controlling devices via a network, a device control method, a client apparatus, and a device control system.
2. Description of the Related Art
With the widespread use of networks, there has been disclosed a device server configured to enable a device (peripheral device), which has conventionally been used by local connection e.g. to a personal computer (PC), to be used by a client PC on a network.
For example, there have been proposed some methods for enabling a client PC on a network to use a device, such as a printer, a storage, or a scanner, as a shared device via a device server.
As one of the methods, a method has been proposed in which dedicated application software (hereinafter referred to as “the utility”) is preloaded in a client PC, and in the case of accessing a device, a user operates the preloaded utility, thereby causing the client PC to virtually recognize the device to be accessed, as a locally connected device, so that the user can access the device as if it is a locally connected device, from the client PC on a network.
In this method, which requires session (connection) start and end operations by a user, the session with a device server is occupied until the user executes an operation for terminating the session with the device using the utility, which disables use of the device by another client PC.
To solve the above-mentioned problem, there has been disclosed a network file management system in which a device server permits a specific client PC to perform data transmission with a device only for a time period during which block data having a data length specified by a block header is transmitted, regarding that the device server is in a data transmission occupation state (see e.g. Japanese Patent Laid-Open Publication No. 2007-317067).
Certainly, the network file management system disclosed in Japanese Patent Laid-Open Publication No. 2007-317067 makes it possible for a plurality of client PCs to share a device without execution of manual operation on the client PCs.
However, in a case where a device is connected which very frequently necessitates the state of occupation by a client PC, it is difficult for the client PC to use another device simultaneously due to a technical restriction that in a state where a client PC occupies one device connected thereto via a network, the client PC cannot use another device.
For example, in the case of using a device, such as an IC card reader, it is required to periodically make a query (polling) as to whether or not the IC card has been detected, i.e. to carry out a device monitoring process (change-of-state detection process) periodically. In general, the device monitoring process is executed by a device driver installed in a client PC.
For this reason, the device is frequently occupied by the client PC via the network, and traffic on the network markedly increases during the occupation of the device. Therefore, it is desirable that the occupation of the device is minimized.
Further, in a state where a device is frequently occupied and data is always flowing over the network, data is vulnerable to hacking. This is undesirable in terms of security.
In addition, when the above-mentioned device monitoring process (change-of-state detection process) is configured such that a device server stores only trigger detection algorithms applicable to specific devices, so as to eliminate model-dependence which makes processing different on a device-by-device basis, the device server loses its flexibility. On the other hand, when trigger detection algorithms applicable to various devices existing in the system are all stored in a device server, it is possible to maintain the flexibility of the device server. However, the device server needs a large-capacity storage area, which causes an increase in costs.